With the advent of modern mobile wireless communication, reducing the power consumption by a receiver in a mobile device is essential in increasing the battery life of the mobile device. One scheme for reducing receiver power consumption involves decoding transmission packets before they have been completely received and powering down the receiver from the time of successful decoding until the end of the packet transmission. However, when multiple packets are simultaneously transmitted, the receiver can only be powered down when all of the packets have been successfully decoded prior to their complete reception. In some situations, when the exact number of packets transmitted is not known to the receiver, all possible decoding hypotheses of the possible number of packets is performed for detecting the exact number of transmission packets. In these cases, if some transmission packets successfully decoded early but some are not, a decision must be made as to whether the early decode failures were due to the fact that the corresponding transmission packet was not transmitted or because the receiver has not yet received a long enough portion of the transmission packet for successfully decoding. In the former situation, the receiver can be powered down early but in the later situation, powering down the receiver would lead to varying unintended consequences. As a result, an incorrect decision to shut down the receiver will result in loss of some packets, while an incorrect decision to keep the receiver on results in a lost opportunity to reduce receiver power consumption. Since transmission packet loss causes severe consequences, successful implementation of receiver shut down requires a good detector that minimizes the probability of false-alarms (detection of packet transmission when no packet was transmitted).
In the context of WCDMA R99 downlink, frequent transmissions of data packets on a Dedicated Transport Channel (DTCH) occur concurrently with sporadic transmission of control packets on a Dedicated Control Channel (DCCH). With blind transport format detection (BTFD), the user equipment's (UE) receiver does not know in advance whether the DCCH is being transmitted at any given time. Upon early decoding of the DTCH, the receiver must then decide whether or not a DCCH packet was being transmitted at that time before it can power down. Such a decision is required even outside the context of early decoding in order to determine the power-control outer-loop signal-to-noise (SNR) target adjustment. In other words, the SNR target must be raised if a DCCH packet was transmitted and failed to decode, but it must not be raised if the decode failure was simply due to absence of packet transmission.
Thus, aspects of this invention provide an apparatus and method for improving the power consumption of a UE upon detection of a DCCH transmission packet.